Permanent-magnet display signal



phone and Telegraph Corporation, New York, N. Y., a corporation of Maryland Application May 15, 1957, serial N6. 659,256 3 Claims. or. 346-678 This inyention relates to apermanent-m'agnet display signal, particularly asignal of this type which employs a two-position bi-stable display :mem'ber, or indicator, pivoted to rotate back and forth between two positions. its principal object is to provide a new and improved signal of the above character which is both highly sensitive and reliable in operation and economical to manufacture.

in lo ovvn permanent-magnet signals of the above type, the rotatable indicator is itself the permanent magnet of the structure, or has the permanent magnet 'fixed therewith and carried thereby. The indicator is mounted near one pole of an electrom'agnet and is operated from either position to the other responsive to a temporary energization, in the corresponding direction of the electromagnet. A

These known display signals have two pronounced disadvantages, in that (1) stray magnetic fields, as from one signal to another, often either inhibit the intended operation or induce a false operation, and (2) the device is relatively 'ineflicient and insensitive because the required angle of rotation of the indicator, about 90 degrees or more, renders the device less efficient and less sensitive than a structure wherein the permanent-magnet armature rotates through a smaller angle.

According to the invention, both of the noted disadvantages of the prior-art structures are substantially overcome by (l) 'pivotall'y mounting the permanent magnet armature 'oftlie structure separately from the indicator and providing an angle-multiplying coupling be tween them, whereby the required angle of movement of the armature is greatly lessened, and by (2) locating the armature within the confines of a space between magnetic members comprising extensions of the respective poles of the electromagnet, whereby efiicint'double-pole short stroke armature operation is obtained, and the noted magnetic members act to shield the armature against stray fields. I

An additional feature of the invention is that efiiciency and sensitivity are promoted by providing a separate armature-starting spring member for each stable position of the. armature tending to move the armature toward the opposite position, but having only a limited armaturefollowing action. These armature-starting spring members conveniently form respective parts of the circuitcontrol switching assemblies often required to be actuated by armature movement. V

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood, by reference to the following description of an embodiment of the invention taken in com junction with the accompanying drawings comprising Figs. 1 to 5, wherein: I

Fig. 1 shows a top view of the permanent magnet signal;

Figs. 2 and 3 show front and bottom views, respec assess Patented Dec. 30, 195 8 2 tively of the signal, Fig, 3 showing only the indicator assembly portion 200; 1 I I Fig. 4 shows a portion of the indicator assembly 200 of Fig. 1 cut along lines 4 4; and

Fig. 5 shows a schematic diagram of a typical circuit employing the signal.

Referring now in particular to Figs. 1' and 2, the device shown therein comprises an electromagnet portion and indicator assembly portion 200.

The electromagnet portion 100 includes a high permeability core member 10 having a chambered portion near both ends for receiving respective forward and rear headers 12 and 13 to define the space for confining the electromagnet coil 11, which, as will hereinafter be described with, reference to Fig. 5, includes two separate windings. Therear header 13 has anumber of terminals 1'4 thereon towhichthewires of the windings of coil 11 are terminated for external connections. The forward header 12 is adapted to receive the indicator assembly portion 200-, as will behereinafter described Core 10 has both of its ends threaded to facilitate the securing of respective pole pieces 15 and 45 thereto, pole piece 15 being secured to core 10 near rear header 13 by washer 18 andnut 19, and pole piece 45 (Fig. 4) being secured to core 10 near forward header 12 by nut47. t .6

Pole piece 15 extends from rear header 13 to forward header 12, outside the periphery of the windings 11, and as shown in Fig.4 is generally U-shaped to substantially encircle the permanent magnet portion of the indicator assembly 2%, the forward end of piece 15 being held securely in position by slots provided in both sides of header 12. This structure shields the armature from any stray magnetic fields and also restricts the magnetic field of the permanent magnet 25. w

Pole piece 15'is provided with separately adjustable screws 16 and 66 which concentrates the generated flux attwo fixed points, these points serving as the salient poles for the rear pole of core 10. These adjustable poles permit variations in, the length of the operating gaps between pole piece 15 and pole piece 45.

Pole piece 45,. as shown in Figs. 2 and 4, is similar to piece 15 in width and thickness and is generally U- shaped, the upward extending tabs 55 and 65 serving as the salient poles for the forward pole of core 10.

When constructed as described, energization of winding 11 results in generated magnetic flux being generally restricted to the path defined by magnetic structures 15 and 45 and the air gap at the forward end of the electromagnet between structures 15 and 45. The fiux passing through structures 15 and 45 is concentrataed at poles 16 and 66 and at poles 55 and 65, the polarity of poles 16 and 66 being opposite that of poles 55 and 65. A reversal in the direction of the current flow through coil 11 results in the generation of magnetic flux of a direction such that the polarity of the pairs'of poles 15, 45, and 16, 66 is reversed.

The indicator assembly portion 200, secured to forward header 12 'by mounting brackets 20 and 24, and their respective screws 17 and 23, includes permanent magnet cradle or armature assembly 26 and indicator assembly 30.

The armature assembly 26 includes 'a cradle 76 of nonmagnetic material, an axle 2.7 secured thereto, and a cylindricalshaped permanent magnet 25 secured'to and carried by cradle 76. Bushings 21 and 41, secured in mounting brackets 20 and 24 respectively, provide pivot points for axle 27which rotatably'secures the armature assembly between'thernoun-ting-brackets 20; and 24. The armature assembly 2-6 also includes "an indicator lever 28 of non-magnetic material 'which'is'secured to cradle 76 and extendsnpwardly and outwardly from the armature provide a bearing surface for axle 22 which has one end j securely fixed to mounting bracket 20, as by press fit. The axle 22 passes through bushing 34 and has its free end crimped flat thus permitting free rotation of indicator 30 therearound, but preventing its removal therefrom. A post 33 passes through indicator 30 below bushing 34 and extends outward beyond the side of indicator 30 to engage lever 28, as previously noted. It can thus be seen that when assembled as described, rotation of permanent magnet 23 and its supporting cradle 76 causes indicator lever 28, by camming actions against post 33, to cause indicator 30 to revolve. The length of lever 28 and the location of post 33 is such that rotation of magnet 25 through given angle results in the rotation of indicator 30 through an angle approximately twice as large in order to overcome the noted disadvantages resulting from longstroke armature operation. As seen in Fig. 1 or 3, the terminating edges of portions 31 and 32 of indicator 36 are arranged to abut the magnetic structure near screws 16 and 66 to limit the noted angle of rotation of the indicator, thus serving as stops for the armature assembly 26.

Armature-starting springs 37 and 67 (Figs. 2 and 3), secured to a terminal 14 of rear header 13 by collar 46, extend forward along the electromagnet portion 100 of the device and terminate near lever 28 of the indicator assembly portion 200. The springs are tensioned inwardly and so formed to abut the portions 78 of arm 28. Contact posts 70 and 90, in addition to forming a contact member of the switching arrangement as will hereinafter be described, serve as stops for respective springs 37 and 67, restricting their inward movement.

With the indicator in its illustrated position, the N pole of permanent magnet is in close proximity with pole 16 of magnetic structure 15 and the S pole is in close proximity with the pole 65 of magnetic structure 45. In such condition, portion 32 of indicator is visible when viewed directly from the forward end of the signal, as through a circular opening in a covering plate or panel 88 which normally conceals the entire signal, excepting for the indicator. With the winding 11 deenergized, the magnetic flux from magnet 25 passes through pole 16, magnetic structure 15, core 10, and pole 65 of structure 45, resulting in magnet 25 exerting a force tending to prevent any rotation therefrom. However, as illustrated in Fig. 3, spring 67 is in abutment with lever 28 and exerting a force counteracting the magnetic force exerted by magnet 25, the force from the spring tension being less than the magnetic force from the magnet 25, thus the armature assembly remains in its illustrated position. When the indicator assembly is rotated into its alternate position, a similar balance of forces are present from spring 37 and magnet 25.

Assuming current is temporarily passed through the winding 11 in a direction such that resulting magnetic flux generated tends to cause poles 55 and 65 to assume a polarity the same as that of the S pole of the permanent magnet 25, this flux tends tocause poles 16 and 66 to assume a polarity in direct opposition thereto. This generated flux is in opposition to the permanent magnet flux and thus the resulting magnetic force is decreased to a point where the force exerted by the concerned spring is predominant, forcing rotation of the armature assembly. When pole N of magnet 25 is moved closer to pole 55, and pole S of magnet 25 is moved closer to pole 65, the magnetic attraction becomes great enough that continued rotation is maintained, and assembly 26 assumes its alternate position causing lever 28, by camming action against post 33, to rotate the indicator to its alternate position, such that portion 31 of the indicator is now visible when viewed directly from the front end of the signal through the opening in panel 88. The magnet and indicator will remain in their last noted position after winding 11 is deenergized by the magnetic flux from magnet 25. When the current through winding 11 is reversed, causing a reversal in the polarity of the pole sets 16, 66 and 55, 65, the indicator will be returned to its illustrated position.

The permanent magnet signal is provided with switching contacts which are actuated when the indicator is rotated from one position to another. This switching arrangement, as shown most clearly in Fig. 4, includes an L-shaped terminal plate 36 having contact posts 40 and 70 secured thereto at one end and having contact post 80 attached thereto at the other end, and includes a terminal plate 35 having contact post 90 secured thereto. Each of the plates 35 and 36 have apertures 77 to which external wires may be attached. As shown in Fig. 3, spring 67 is out of contact with post 90 and spring 68 is out of contact with post 80, spring 68 having an upwardly extending portion engaging spring 67, causing it to follow any outward movement of spring 68. As hereinbefore described, springs 67 and 68 are tensioned towards the center of the indicator assembly 200, and thus when the indicator is revolved, springs 67 and 68, by following action, make contact with respective posts 90 and 80.

'In a similar manner, springs 37 and 38 are secured to a terminal 14 and extend forward to engage the lever 28 when it is moved to its alternate position, such engagement moving the springs 37 and 38 out of contact with respective contacts posts 70 and 40. Thus, when the indicator of the signal is in its normal illustrated position, post 70 is electrically connected to post 40 thereby establishing electrical contact between terminal plates 35 and 36, and when the indicator is rotated to its alternate position, such electrical contact is broken. Also, springs 67 and 68, come into and out of engagement with respective posts 90 and 80 to make and break electrical contact between terminal plate 36 and the terminal 14 which secure springs 67 and 68 to the signal. The two sets of springs when used in conjunction with their respective terminals 14 and contacting plates 35 and 36 are thus adaptable to numerous switching arrangements.

Referring now to Fig. 5 of the drawings, the schematic drawing of a typical circuit employing the permanent magnet signal will be described. In Fig. 5, the coil 11 of Figs. 1 and 2, is shown as comprising two magnetically opposing windings 1 and 2 in order to provide the hereinbefore-noted polarity reversals of the poles of the electromagnet.

Responsive to the initiation of a call from station S on line L1, current flow over the line loop from battery 502 through break contacts 1 of jack OJ, the line winding 1 of signal EM and ground through break contacts 2 of jack OJ, energizes windingl. Assuming the current flow therethrough to be of a direction which causes indicator 30 to be rotated from its illustrated position to its alternate position in the manner hereinbefore described, electrical contact is made between contact members and 90, and indicator 30 gives a visual indication to an attending operator that a call exists on line L1.

Responsive to electrical contact between post 80 and 98, current flows from battery through winding 2 of electromagnet EM and through resistor 501 to ground. As indicated, windings 1 and 2 are wound in opposition so that the magnetic flux generated by each opposes that of the other. However, the magnetic flux generated by winding 2, the current through the winding being limited by resistor 501, is insufficient to reduce the resultant flux such that the tension of spring 37 restores the indicator to its normal unoperated position. Thus the indicator and magnet remain in their last-assumed position.

When the operator observes the calling condition on line L1, connection is made thereto by inserting the usual answering plug (not shown) into jack OJ, which opens contacts 1 and 2 of jack OJ and disconnects the windings of signal EM from the line conductors. At such time, winding 1 is deenergized but the operated contacts 80 and 90 maintain current flow through winding 2 over the hereinbefore-traced path. The flux generated by Winding 2 is of a polarity opposite to that which caused the indicator to assume its present position, and consequently, the indicator is restored to its normal illustrated condition by the resulting change in the polarity of the poles of the electromagnet.

After disconnect by the operator, the windings of the signal are again connected to the line conductors by contacts 1 and 2 of jack OJ. In the event the subscriber at station S has already disconnected, no current flows through the windings of the signal and it is left in its illustrated non-calling position. If the subscriber has not disconnected at the time the operator disconnects, the signal EM indicates a call in the manner hereinbefore described. Responsive to subsequent subscriber disconnect, winding 1 becomes deenergized but winding 2 is maintained energized from current flow through contacts 80 and 90 and the resultant flux is of a polarity which causes the indicator to restore to its normal unoperated position. When restored, contacts 80 and 90 are opened and winding 2 of the signal becomes deenergized.

While I described the principles of my invention in conjunction with specific apparatus it is to be clearly understood that this invention is made only by way of example and not as a limitation to the scope of my invention.

We claim:

1. A polarized electromagnetically actuated device for displaying alternative signals, comprising in combination an electromagnet having an elongated armature pivoted for a back-and-forth turning movement about its center through a relatively small angle from either occupied one of two alternative positions to the other in response to the corresponding one of two oppositely poled energizations of the electromagnet, the armature comprising a permanent magnet the ends of which describe relatively short diametrically opposed arcs as the armature moves back and forth between positions, pole members connected with the opposite pole ends of the electromagnet and providing four pole faces each located near a separate one of the ends of the said arcs and slightly spaced outwardly therefrom out of reach of the armature, the pole faces at the ends of either arc being connected by respective pole members to opposite pole ends of the electromagnet, with either pole face at either are being connected to the same pole end of the electromagnet as the nearer pole face at the other are, a display member and means fixed with the electromagnet for pivotally mounting the display member for a turning movement through a relatively large angle from either occupied one of two alternative display positions to the other, with the display positions corresponding respectively to the said armature positions, and means coupling the display member to the armature for a movement of the display member from either position to the other in response to a corresponding movement of the armature, the coupling means including a relatively long-lever-arm coupling member carried by the armature and a cooperating relatively short-lever-arm coupling member carried by the display member, to cause the relatively small angular movement of the armature from either of its positions to the other to bring about the larger angular movement required by the display member in rotation between its respectively corresponding positions.

2. An elecromagnetically actuated device for displaying alternative signals, comprising in combination a relatively elongated electromagnet having and elongated armature located with its center in general alignment with the forward end thereof and pivoted for a turning movement about its center from either occupied one of two alternative positions to the other in response to the corresponding one of two oppositely poled energizations of the electromagnet, the armature comprising a permanent magnet the ends of which described relatively short diametrically opposed arcs as the armature moves back and forth between positions, pole members connected with the opposite pole ends of the electromagnet and providing four pole faces each located near a separate one of the ends of the said arcs and slightly spaced outwardly therefrom out of reach of the armature, the pole faces at the ends of either arc being connected by respective pole members to opposite pole ends of the electromagnet, with either pole face at either are being connected to the same pole end of the electromagnet as the nearer pole face at the other arc, the said pole member which is connected to the rearward pole end of the electromagnet encompassing the armature and the other pole member to shield the armature from stray magnetic fields, a non-magnetic display member and means fixed with the electromagnet for pivotally mounting the display member in general alignment with the electromagnet and armature and forwardly of the armature for a turning movement from either occupied one of two alternative display positions to the other, with the display positions corresponding respec tively to the said armature positions, and non-magnetic coupling means extending between the armature and the display member and serving to couple the display member to the armature for a said turning movement of the display member from either position to the other in response to a corresponding movement of the armature.

3. An electromagnetically actuated device for displaying alternative signals, comprising an electromagnet having armature-control pole members and having a magnetically polarized armature pivoted for a turning movement between the pole members from either occupied one of two oppositely poled positions to the other in response to the corresponding one of two alternative energizations of the electromagnet, such armature positions corresponding respectively to the said pole members, a display member and means for driving it by armature movement to occupy display positions corresponding respectively to the said armature positions, the armature being magnetically polarized sufiiciently to cause it tobe held magnetically between energizations in either of its said positions by flux traversing the armature and the nearer pole member, the polarization of the armature also acting in aid of the said rotation of the armature in response to a said corresponding energization, a separate armature-starting spring for each of said armature positions tensioned responsive to the rotation of the armature into such position to urge the armature back toward its alternate position, whereby armature'movement from an occupied position is started by a combination of spring action and polarized electromagnet action.

References Cited in the file of this patent UNITED STATES PATENTS 1,623,950 Sargent Apr. 5, 1927 1,754,868 Wehling Apr. 15, 1930 2,644,939 Ebel et a1. July 7, 1953 2,680,970 Durkee June 15, 1954 2,740,956 Hatton Apr. 3, 1956 

